山东省海阳市土堆金矿床地质特征

山东海阳土堆金矿床主要赋存于荆山群野头组及侵入其中的新元古代九曲单元二长花岗岩中。矿体多为脉状或透镜状；矿石矿物成分简单，金属矿物以黄铁矿为主，金矿物以自然金、银矿为主。通过分析成矿控制条件认为：荆山群分布区是寻找该类型金矿的地层标志；NE向的断裂带中，绢英岩化、绿泥石化、钾化、硅化、黄铁矿化等蚀变特征是寻找金矿(化)体的围岩蚀变标志，新元古代岩体及燕山晚期脉岩发育是寻找该类金矿的岩浆岩标志。     

A New Inversion Method of Sedimentary Strata For Deriving Double Parameters and Its Applications

The inverse problem of wave equation is the importance of study not only in seismic prospecting but also in applied mathematics. With the development of the research, the inverse methods of 1 - D wave equations have been trending towards the multiple parameters inversion . We have obtained an inverse method with double -parameter, in which medium density and wave velocity can be derived simultaneously. In this paper, to increase the inverse accuracy, the method is improved as follows. Firstly, the formula in which the Green Function is omitted are derived and used. Secondly, the regularizing method is reasonable used by choosing the stable function. With the new method, we may derive elastic parameter and medium density or medium density and wave velocity. Thus, lithology parameters for seismic prospecting may be obtained.After comparing the derived values from the new method with that from previous method, we obtain the new method through which substantially improve the derived accuracy . The new method has been applied to real depths inversion for sedimentary strata and volcanic rock strata in Chaoyanggou Terrace of Songliao Basin in eastern China. According to the inverse results,the gas - bearing beds are determlned.     

Metamorphism and microstructures along a high-temperature metamorphic field gradient: the north–eastern boundary of the Královský hvozd unit (Bohemian Massif, Czech Republic)

A metamorphic field gradient has been investigated in the Moldanubian zone of the central European Variscides encompassing, from base to the top, a staurolite–kyanite zone, a muscovite–sillimanite zone, a K‐feldspar–sillimanite zone, and a K‐feldspar–cordierite zone, respectively. The observed reaction textures in the anatectic metapsammopelites of the higher grade zones are fully compatible with experimental data and petrogenetic grids that are based on fluid‐absent melting reactions. From structural and microstructural observations it can be concluded that the boundary between the kyanite–staurolite zone and the muscovite‐ and K‐feldspar–sillimanite zones coincides with an important switch in deformation mechanism(s). Besides minor syn‐anatectic shearing (melt‐enhanced deformation), microstructural criteria point (a) to a switch in deformation mechanism from rotation recrystallization (climb‐accommodated dislocation creep) to prism slip and high‐temperature (fast) grain boundary migration in quartz (b) to the activity of diffusion creep in quartz–feldspar layers, and (c) to accommodation of strain by intense shearing in fibrolite–biotite layers. It is suggested that any combination of these deformation mechanisms will profoundly affect the rheological characteristics of high‐grade metamorphic rocks and significantly lower rock strength. Hence, the boundary between these zones marks a major rheological barrier in the investigated cross section and probably also in other low‐ to medium‐pressure/high‐temperature areas. At still higher metamorphic grades (K‐feldspar‐cordierite zone), where the rheologically critical melt percentage is reached, rock rheology is mainly governed by the melt and other deformation mechanisms are of minor importance. In the study area, the switch in deformation mechanism(s) is responsible for large‐scale strain partitioning and concentration of deformation within the higher‐temperature hanging wall during top‐to‐the‐S thrusting, thus preserving a more complete petrostructural record within the rocks of the footwall including indications for a ?Devonian high‐ to medium‐pressure/medium‐temperature metamorphic event. Thrusting is accompanied by diapiric ascent of diatexites of the K‐feldspar‐cordierite zone and infolding of the footwall, suggesting local crustal overturn in this part of the Moldanubian zone.     

陕西淳化圣人桥平缓盖层中复杂褶皱的成因——兼论重力滑动构造的分类

陕西圣人桥附近,复杂多样的褶皱出现在平缓的地台盖层之中。对其成因,争议颇多,或认为推覆作用所致,或认为受断裂作用控制。笔者通过详细研究,认为这些复杂褶皱是一种水底重力滑塌构造。据此,还提出了重力滑动构造新的分类,即重力蠕滑;重力滑塌以及重力滑碎等三类。     

Prograde pressure–temperature paths in the pelitic schists of the Sambagawa metamorphic belt, SW Japan

Prograde P–T paths recorded by the chemistry of minerals of subduction‐related metamorphic rocks allow inference of tectonic processes at convergent margins. This paper elucidates the changing P–T conditions during garnet growth in pelitic schists of the Sambagawa metamorphic belt, which is a subduction related metamorphic belt in the south‐western part of Japan. Three types of chemical zoning patterns were observed in garnet: Ca‐rich normal zoning, Ca‐poor normal zoning and intrasectoral zoning. Petrological studies indicate that normally‐zoned garnet grains grew keeping surface chemical equilibrium with the matrix, in the stable mineral assemblage of garnet + muscovite + chlorite + plagioclase + paragonite + epidote + quartz ± biotite. Pressure and temperature histories were inversely calculated from the normally‐zoned garnet in this assemblage, applying the differential thermodynamic method (Gibbs' method) with the latest available thermodynamic data set for minerals. The deduced P–T paths indicate slight increase of temperature with increasing pressure throughout garnet growth, having an average dP/dT of 0.4–0.5 GPa/100 °C. Garnet started growing at around 470 °C and 0.6 GPa to achieve the thermal and baric peak condition near the rim (520 °C, 0.9 GPa). The high‐temperature condition at relatively low pressure (for subduction related metamorphism) suggests that heating occurred before or simultaneously with subduction.     

Strata Architectural Variability and Facies Distribution in a Structural Transfer Zone:A Case Study of Fushan Sag,Northern South China Sea

Structural transfer zones in a half-graben rift basin play a significant role in controlling sandy sediments and providing a target for hydrocarbon exploration. Previous studies have classified the transfer zone in lacustrine environments into two different patterns: synthetic approaching transfer zones and synthetic overlapping transfer zones. However, the evolution of the depositional pattern and the controlling factors of the above transfer zones are still unclear. In the Fushan Sag, the northern South China Sea, an overlapping transfer zone developed in the early Eocene Epoch, while a synthetic approaching transfer zone developed in the late Eocene, due to tectonic uplift. This evolutionary process provided an opportunity to study the stacking pattern of strata architectural variability and facies distribution in the structural transfer zone of the Eocene lacustrine basin. In this study, following the indications of the oriented sedimentary structures in core samples and heavy mineral assemblages of 18 wells, the evolution of the paleo-hydrodynamic distribution during the early and late Eocene has been reconstructed. The sequence-stratigraphy was then divided and the sand body parameters calculated, according to the seismic data and well log interpretations. During the early Eocene, the lake level was at a low stand, the faults broken displacement in the East block being over 50?m. The prograding delta and turbidites are oriented perpendicular to the structural transfer zone. According to the quantitative analysis of the flow rate and the depositional parameters, we speculate that gravity transportation of the sediment and the sediment-supply are the dominating factors during this period. Up to the late Eocene, the rising lake level and the decreased fault displacement leads the flow to divert to a NE-direction, resulting in it being parallel to the axis of the transfer zone. Thus, we speculate that the accommodation space is predominant in this period. In comparison with the above two periods, a braided river delta with an isolated sand body and turbidites developing in the deep area is prominent in the overlapping transfer zone, while a meandering river delta is characteristic of the synthetic approaching transfer zone.     

Formation Time of the Kalaqin Metamorphic Core Complex: Constraints from Zircon DatingEI北大核心CSCD

The Kalaqin metamorphic core complex, located on the northern margin of the Yanshan Tectonic Belt, is an important structure to understand the Late Mesozoic destruction processes of the North China Craton. In this study, structural analysis and geochronological investigation were conducted for the Anjiayingzi pluton and associated granodiorite dikes that intruded the core complex. Field observations demonstrated that emplacement of the pluton and dikes took place after the early stage extensional deformation, and intrusions are products of syn-tectonic magmatism during the late stage extension deformation. LA-ICP-MS zircon U-Pb dating yielded ages of 133-131 Ma for the Anjiayingzi pluton and 135 Ma for the dike, which demonstrated that the early extensional deformation took place at 156-135 Ma, rather than the Early Cretaceous as proposed previously. By integrating with other dating results, the early extensional deformation occurred at 156-150 Ma (Late Jurassic) and led to the exhumation of the core complex. The core complex was overprinted by a late extension in the Early Cretaceous. The revision of formation time for the Kalaqin metamorphic core complex further confirms that the extensional deformation took place in the Late Jurassic in the Yanshan tectonic belt, and therefore, it is likely that the northern margin of the North China Craton might have destructed since the Late Jurassic. © 2018, Science Press. All right reserved.     

辽西义县组早期火山事件层地球化学特征及意义

义县盆地早白垩世义县组为一套火山-沉积岩系,沉积层中多含凝灰质成分。为了解沉积期火山活动对沉积层产生的影响,对砖城子层火山碎屑泥灰岩(火山事件层)和纹层状泥灰岩夹层、大康堡层纹层状泥灰岩进行岩石学和地球化学的研究。研究表明:火山事件层中含大量的火山碎屑(20%±),其他各层均含凝灰质成份。样品中主量元素Ca O、Mg O和Si O_2含量较高,Si O_2含量变化较大,Al_2O_3含量较低;微量元素与上地壳(UCC)元素比值多小于1,大多数微量元素(Rb、Th、Nb、REE等)处于亏损状态,火山事件层富集Li、Sc、As、Sr和Ag元素。沉积期火山活动对沉积层中Si O_2和K_2O含量影响较大,并可能导致As元素富集。火山事件层样品化学风化指数(CIW)在82~91之间,呈逐渐增加的趋势,指示风化作用强烈。     

西藏措勤盆地上侏罗统吐卡日组上下段的厘定及其礁灰岩发现的油气勘探意义

西藏班戈县保吉地区各昌茶玉剖面发现晚侏罗世珊瑚化石约12属16种,分别为Calamophylliopsis?sp.,Clausastraea?sp.,Epistreptophyllum cylindratum Milaschevitsch,Epistreptophyllum sp.,Heliocoenia aff.etalloni Koby,Kobyastraea?sp.,Montlivaltia tenuilamellats Roniewicz,Montlivaltia?sp.,Myriophyllia?sp.,Pseudocoenia hexaphyllia(d’Orbigny),Pseudocoenia?sp.,Rhipidogyra?sp.,Stephanastraea?sp.,Stylina?sp.,Stylina cf.subramosa de Fromentel,Thecosmilia?sp.等。化石指示各昌茶玉剖面上部第42—80层时代为晚侏罗世牛津期—基默里奇期,表明各昌茶玉剖面地层并不属于原划的中二叠统下拉组。本文依据化石及岩性特点将其修订为上侏罗统吐卡日组。根据保吉地区的吐卡日组与上下地层的接触关系及其岩性变化可划分为上下两段地层,各昌茶玉剖面代表吐卡日组下段地层,主要为厚层碳酸盐岩夹少量泥页岩及多层礁灰岩。久朗仓剖面代表吐卡日组上段地层,为一套碳酸盐岩夹大量粗碎屑岩地层。吐卡日组下段在措勤盆地内部、班公湖—怒江缝合带内广泛分布,指示晚侏罗世措勤盆地发育大面积广阔稳定的碳酸盐岩台地,其中生物礁表明晚侏罗世碳酸盐岩台地具有优越的油气生成和储集条件。